The present invention relates to a display device making it possible for a user to observe a synthetic light image superimposed in his natural field of vision.
Numerous devices of this kind are already known, which can be used in vehicles and, in particular, in aircraft.
These devices usually called head up sights or head down sights depending on their implantation necessarily comprise a means for forming an image such, for example, as a cathode ray tube or a liquid crystal cell, this means being mounted on a support fixed to the vehicle, and an optical mount including collimation means as well as at least one partially reflecting mirror which extends into the field of vision external to the user for making said superimposition possible.
Of course, the means for forming the image must be connected by electrical connections to an electric power supply source and/or to a symbol generating device. In wide angle sights, the optical mount is necessarily bulky and consequently space consuming.
When they are fixed permanently and are not used, these devices become particularly troublesome. Besides the disadvantages resulting directly from the space they take up in the restricted volume of the piloting cabin, they partially attenuate the vision of the pilot towards the outside.
This is why users frequently ask for the possibility of retracting these devices when their use is not necessary.
Now, that implies the provision of a structure with appropriate kinematics to make such retraction possible and guaranteeing strict positioning of the optical mount during use. Furthermore, the problem raised by the electric connections of the image forming member, during such retraction, must be solved.
All these requirements lead then very often to heavy and bulky devices, difficult to integrate in small aircraft.